Circuit Description

WARNING: This page is about a different variant/trim than selected.

VCM supplies a voltage of about .45 volt between HO2S signal and HO2S ground circuits. HO2S varies voltage from about one volt with rich exhaust to .1 volt with lean exhaust. VCM monitors activity for 100 seconds after closed loop. During monitored period, VCM counts how often HO2S switches between rich and lean. VCM determines average switching time. If average switching time is too slow, DTC P0133 will set.

HO2S produces no voltage and acts as an open circuit when temperature is less than 600°F (316°C). HO2S heater provides for faster sensor warm-up allowing sensor to become active in a shorter period of time and remain active during long extended idle. DTC determines if HO2S is operating properly by checking response time.

DTC will set when the following conditions are present:

No ECT, EVAP, IAT, MAF, MAP or TP sensor DTCs are set.
No intrusive test is in progress.
No device controls are active.
System voltage is at least 9 volts.
HO2S transition time from lean to rich is greater than 85 milliseconds.
HO2S transition time from rich to lean is greater than 85 milliseconds.